The subject invention relates generally to recorders for producing a hard copy of data supplied in electrical line format and more particularly to apparatus for electrographic recording or printing graphical information or other alphanumerical data.
The electro recording apparatus and processes of the prior art is generally characterized by (1) electrically charging areas on selected portions of a recording medium, (2) developing the charged areas on the recording medium, and (3) fixing the developed areas on the recording medium, as by pressure and/or heat, to render the recorded information permanent on the medium. The subject invention is directed to improving the first of the above characterized portions, namely the electrically charging of the areas on the recording medium.
Various techniques and apparatus have been arrived at for producing a hard copy of data supplied in electrical line format wherein electrostatic charges on the recording format are established. U.S. Pat. No. 3,757,352 to Murray et al exemplifies a system wherein a conductive paper web with a dielectric coating is fed over a writing roll where its surface receives image defining electrostatic charges deposited by one of three pulsed line scan styli bearing directly and successively upon it, the styli being removably secured to an endless belt moving at a constant velocity laterally of the web. Another example is the teachings of U.S. Pat. No. 3,050,580 to Schwertz or U.S. Pat. No. 2,743,989 to Clurman et al, the former having plural fixed point electrodes arranged in a transverse row across a web upon which an image defining electrostatic charges are deposited and the latter which has plural electrodes mounted serially on an endless belt moving laterally of the web. Such prior art is, however, relatively complex and expensive, and have generally suffered, in varying degrees, from a number of drawbacks due to environmental conditions, dependency on critical tolerances, etc. to list but a few. Other drawbacks are the problems of synchronization required of copiers where copy quality is most desirable.
Another disadvantage of these prior art copiers which utilize endless belts is that pulleys utilized to carry and drive these endless or continuous belts are usually crowned so that at operating speeds the crowns alone are sufficient to hold the belt in proper position. Additionally, these copiers generally utilize magnetic retaining means to prevent flutter of the stylus assemblies as it traverses around the pulleys. Crowning of the pulleys however, causes the belts to become different in form after periods of use whereas the magnetic retaining means add complexity, hence cost, to the copiers.